In this study, pedigree data of 7170 lambs produced from 177 rams and 2182 ewes collected during 1989 to 2009 in the Shirvan Kordi sheep breeding station, were used for calculating inbreeding coefficients. The impact of inbreeding on the studied traits was investigated by including inbreeding coefficients for each animal as a covariate in the animal model. Average inbreeding coefficient of the flock in base year, 1989, was estimated as 0.668%. The low average inbreeding in the flock could be ascribed to the structured breeding regime of the station for preventing mating among relatives. Totally, 23.3% of the animals were inbred with average inbreeding coefficient of 2.87%. Out of these, 1668 animals were inbred including 823 males and 845 females with the mean inbreeding coefficients of 2.81% and 2.93%, respectively. Coefficients of inbreeding were also estimated in this population using 6 microsatellite markers (BM8125, BMS2361, BM6526, BM6526, BMS1004 and BM6444) and 100 blood samples. Within population, inbreeding F-statistic (FIS) ranged from -0.1859 (BM6526) to 0.3329 (BM6438). The FIS estimates were positive for BM6438 and BM6444 loci (0.3329 and 0.2287), respectively and estimates for the other loci were negative. Average inbreeding coefficients based on molecular markers was estimated as 0.2617%. Birth weight, weaning weight, body weight at 6 months, body weight at 9 months, body weight at 12 months, annual wool production and number of lambs per ewe lambing were changed by -0.0131, 0.0795, 0.0013, -0.0653, -0.0921, 0.0083 and -0.023 kg, respectively for every one percent increase in inbreeding. تفاصيل المقالة

The aim of this study was to describe inbreeding and population structure in Sangsari sheep breeding station. For this reason, data from 7028 Sangsari sheep which were collected during 1987-2014 in Sangsari sheep breeding station located near to Damghan city, Semnan province were used. Lambs born during 2010-2014 were considered as reference population. The genetic structure analysis of the population was realized by the ENDOG (v.4.8) software. Mean inbreeding of total population and reference population was 0.28% and 0.70%, respectively. Average relatedness, realized effective population size based on individual increase in inbreeding, effective numbers of founders (fe),and founder genome equivalents (fg) were estimated 0.59%, 148.75, 140 and 49.97, respectively. Mean generation interval in present population was 4.24 years and average number of equivalent to discrete generations was estimated as 1.64. Average coancestry, effective number of ancestors (fa) and average equivalent complete generation were calculated 1.0005%, 76 and 3.02, respectively. Ratio of fe/fa which expresses the effect of population bottlenecks was 1.84. 50% of total genetic variation was explained by the 32 most influential ancestors. By monitoring parameters associated with genetic diversity and breeding management, the reduction of genetic diversity and probable harmful effects resulting from excessive increase of inbreeding can be prevented. تفاصيل المقالة